1. Field of Invention
The present invention relates to the field of downhole tools. More particularly, the present invention relates to packers for use in downhole applications.
2. Related Art
Packers are used to seal off the annulus of a wellbore. A packer is typically run into the wellbore and is then set against the casing of a wellbore so that the packer sealing element seals against the wellbore casing and the packer slips are anchored to the wellbore casing. Some packers are retrievable and include a release mechanism. Upon activation of the release mechanism, the sealing element de-energizes and the anchors are released which enables the movement of the packer from its previously set position.
One type of retrievable packer is a shear release packer. A shear release packer includes a shear nut that is sheared by manipulating the tubing string thereby enabling the release of the packer. Some prior art shear release packers are designed so that, when they are set, the load path between the sealing element and the slips travels primarily through the relevant shear nut, which may be located at the lower end of the packer. Unfortunately, in many instances, the pressure difference across an energized sealing element once set is significant. The force exerted on the packer by this pressure difference tends to act on the packer and attempts to move the packer from its fixed location in the wellbore. Thus, if the force acting on the sealing elements is too high (for example, due to a high differential pressure across the sealing element), such force is transferred from the sealing element and primarily through the shear nut, exposing the shear nut to an extremely high force. This force can sometimes prematurely shear the shear nut and release the packer causing a potentially dangerous and costly situation.
The prior art would therefore benefit from a shear release packer that does not suffer from the aforementioned deficiencies.
A shear release packer that includes at least one sealing element, at least one slip, and at least a lower shear nut. In order to release the packer, the lower shear nut is sheared enabling the at least one sealing element to de-energize and the at least one slip to disengage the casing. When set, the packer is constructed to that the lower shear nut is isolated from the load path generated by the forces acting on the at least one sealing element. The load path travels from the at least one sealing element to the at least one slip without having to travel through the lower shear nut.